Air deflectors are commonly employed on caravans and large trucks but it has been found that when they are of a rigid construction they are cumbersome, difficult to attach to a vehicle and equally difficult and inconvenient to store or transport when not in use. One particularly popular and successful configuration of such rigid deflectors is one which assumes the form of a bubble or dome on at least the upper part of the flat frontal surface of a vehicle, usually a trailer or load conveying body projecting above a driver's cab. Because of the difficulties mentioned, these deflectors are almost invariably installed permanently on a vehicle. They are, as far as applicants are aware, simply not regarded as suitable for use removably on a vehicle. To overcome these problems, numerous inflatable and even self-inflating air deflectors have been proposed.
Thus German Offenlegungsschrift DE No. 31.15.742 describes a self inflating air deflector which is located on the rear panel of a truck for reducing drag. The deflector comprises a substantially flexible bag having an inlet located above the roof of the truck. The deflector is held to a particular shape by means of rope attachments to the truck. It is envisaged that the deflector operates adequately but it will be appreciated that the aerodynamics of the front of the vehicle will not be improved. However, the vehicle front is an area providing considerable wind resistance, particularly vehicles having a substantially flat vertical front surface.
German Offenlegungschrift DE No. 25.11.700 describes, amongst other arrangements, an air deflector arrangement in the form of a narrow, inflatable, part circular cross-sectioned, elongate member extending along the top and side edges on the front of a trailer or semi-trailer of a truck. This deflector may have a centrally located inlet with outlets at the bottom of the side regions of the deflector. The inlet and corners of the deflector are rigid. It is a problem with this form of deflector that it is not easily removable and there is generally a substantial outwardly directed force tending to blow the deflector off the trailer or semi-trailer.
U.S. Pat. No. 3,945,677 describes a self inflatable air deflector which fits on the roof of a truck cab to reduce the wind resistance of an associated trailer or semi-trailer. An air inlet is provided which locates above the windscreen of the truck. The deflector has no inherent means of maintaining a stream-lined shape in use and relies on the shape of the cab to maintain some form of streamlining. It is thus envisaged that substantial bulges may form due to the pressure disparity inside and outside of the deflector. Furthermore, the deflector cannot be used on a frontal wall of a caravan nor may it be attached to the frontal wall of a trailer, semi-trailer or transport container, as it will not maintain a streamlined shape.
It is the object of this invention to provide a self-inflating air deflector which may be used on a front surface of a vehicle and which maintains an effective stream-lined shape in use.